Ethylsulfonate-alkylamine copolymers as colorant backbones

ABSTRACT

Ethylsulfonate-alkylamine copolymers are disclosed. These copolymers find special application as intermediates in the preparation of new water-soluble polymeric colorants which are also disclosed, especially water-soluble polymeric colorants for edibles.

This is a continuation-in-part of U.S. Ser. No. 638,731, filed on Dec.8, 1975 and now issued on June 20, 1978 as U.S. Pat. No. 4,096,134.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to certain amine and sulfonate group-containingcopolymers and their use as backbones upon which to build water-solublepolymeric colorants.

2. Prior Art

Polymeric colorants have been widely studied. Ida et al., YakugakuZasshi, 89 (4), 524-30 (1969), were among the first to add polymericcolorants to edibles and show that such colorants are not appreciablyabsorbed from the gastrointestinal tract into the systemic circulationfollowing ingestion. Such a property potentially eliminates any systemictoxicity which might otherwise arise. Dawson et al., in U.S. Pat. No.3,920,855, described additional polymeric colorants for edibles. The Idaet al materials were generally formed by joining together a plurality ofpolymerizable colorant groups into a macromolecule. The Dawson et almaterials were formed from polymeric backbones to which were graftedcolorant groups. The Dawson et al backbones generally carried aminegroups. Gless et al, U.S. Pat. No. 4,018,826, disclosed polyvinylamineas a polymeric backbone for the affixment of colorant groups. Thepresent invention concerns this type of colorant having a differentbackbone.

In many color-use systems, including the great majority of ediblesystems, it is essential that a polymeric color be water-soluble. If thecolorant group itself is very water-soluble, such as those azo colorantswhich carry 1 to 4 sulfonate groups, very likely the resulting polymericcolor will be soluble as well. However, many attractive colorant groupsare not substantially soluble in water. With such groups, watersolubility must be imparted by incorporating separate solubilizinggroups into the polymer backbone. U.S. Ser. No. 638,730 filed Dec. 8,1975, now U.S. Pat. No. 4,051,138, by Wang et al. discloses thesolubilizing method wherein chromophores are attached to anamine-containing polymer and the polymer is then solubilized bysulfamating residual amine groups. Addition of the solubilizing groupshould add a minimum of weight and bulk to the colorant if maximum colorstrength is to be achieved. Likewise, other nonchromophore components,such as the backbone itself, should add minimum weight to the polymericcolorant.

The present invention concerns the use of vinyl sulfonate as a comonomerto impart water solubility to a polymeric colorant. Vinyl sulfonate,##STR1## is commercially available as the sodium salt. Vinyl sulfonatehas been used in the art with added comonomers to form structuralcopolymers and the like.

STATEMENT OF THE INVENTION

It has now been found that copolymers of vinylsulfonate and unsaturatedlower alkylamines are excellent backbones for water-soluble polymericcolorants. Such copolymers offer the advantage of imparting a highdegree of water solubility while contributing a minimum weight to thepolymer.

DETAILED DESCRIPTION OF THE INVENTION The Polymer Backbones

The polymer backbones of this invention are linear copolymers made up ofrepeating ethylsulfonate and alkylamine groups. The sulfonate componentis represented by the formula ##STR2## wherein M⁺ is an alkali metalcation, especially Na⁺, K⁺, or Li⁺. It is referred to herein asethylsulfonate. The term "vinyl sulfonate" is used to refer to itsprecursor, ##STR3## which is the commercially available material whichis formed into the present copolymers.

The other component of the backbone is generally a single alkylaminegroup. Of course, a plurality of amines could be used within the purviewof this invention, but for simplicity, a single amine is generallypreferred. The alkylamines are lower alkylamines, that is amines havingfrom 2 to about 6 carbons per amine group. They should be olefinicallysaturated when present in the copolymer. The amine groups are joinedinto the backbone through carbon-carbon single bonds, not through aminelinks.

Suitable amines in their combined forms include ethylamine,N-methylethylamine, α-methylethylamine, 3-methylpiperidine,β-methylethylamine, butylamine and the like. These suitable amines canbe represented structurally by the formula: ##STR4## wherein each of R₁and R₂ are independently selected from the group consisting of hydrogenand lower saturated alkyls of up to 4 carbon atoms, R₃ is a branched orlinear lower saturated alkyl of from 1 to 4 carbon atoms, and R₄ is acarbon-nitrogen single bond or a 1 to 4 carbon alkyl subject to thelimitation that the total number of carbon atoms in R₁, R₂, R₃, and R₄is not greater than 5. R₂ and R₃ can be joined into a single lower alkylsuch as occurs with 3-methylpiperidine.

The copolymer backbone is represented by the structural formula:##STR5## wherein n and m are integers greater than 1. Preferred aminesare ethylamine, N-methylethylamine and 3-methylpiperidine. For use inthe manufacture of polymeric colorants, the sum of n plus m generally issubstantially greater than 1, such as from about 20 to about 8000,preferably n+m is from about 60 to about 6000 and more preferably fromabout 100 to about 3000. It will be appreciated that any value for n, mor n+m will be an average value and that the actual exact size of anysingle molecular chain will not be precisely known.

The proportions of amines and sulfonates may be varied. A 1:1 copolymer(i.e., n=m) may be prepared or n can equal from about 0.4 to 2.5 timesm. When good water solubility of a colorant is of maximum importance, ngenerally should be not less than about 0.5 m (i.e., from 0.5 to 2.5 m).Most preferably n is equal to 0.6 to 1.5 m.

PREPARATION OF THE BACKBONES

The backbones are prepared by copolymerizing a mixture of vinylsulfonate and an olefinically unsaturated alkylamine or, more commonly,an olefinically unsaturated alkylamine precursor such as an amide. Thiscopolymerization is carried out in liquid phase in the presence of afree radical initiator. Typical useful conditions for polymerization area temperature of from about 40° C. to about 100° C., a reaction time offrom 2 to 100 hours, from about 0.5 to 5%, basis monomer, of a freeradical initiating catalyst such as benzoyl peroxide, AIBN or the like,and an aqueous/organic liquid reaction medium such as a lower alkanolwith water. Such conditions are typical. Other conditions, known to theart as suitable for free radical polymerization, may be employed aswell. Representative preparations are illustrated in detail in thepresent Examples.

COLORANTS BASED ON THE COPOLYMERS

The ethylsulfonate/akylamine copolymers find good application asbackbones for polymeric colorants. In such use, color bodies, hereinreferred to as "chromophores" or "chromophoric groups", are covalentlyaffixed to the copolymer backbones through the copolymer's aminenitrogens.

THE CHROMOPHORIC GROUPS

The chromophoric groups employed in these coloring compositions areorganic optical chromophores. These materials are defined to be organicchemical groups which exhibit a visual color to the human eye whenattached to a polymeric backbone via amine linkages. These chromophorescan be selected from a wide range of classes of groups, including theazo chromophores, anthraguinone chromophores, xanthene chromophores,triphenylmethane chromophores, indigoid chromophores, and the like.These classes of chromophores are merely represenative--other similarmaterials also being usable. Among these chromophores specialpreferences are given to azo chromophores because of the great varietyof technically important clear intense red to yellow colors which theyprovide and to anthraquinone chromophores because of their greatstability under stressful conditions of heat and light and the widerange of colors which they permit. Among chromophores, those which arethemselves water-insoluble generally achieve most improved usefulnesswhen used in the present polymeric form. A chromophore is defined asbeing water-insoluble if its solubility in room temperature water atneutral conditions (pH 7) is less than 500 parts per million weight(basis water). Conversely, a polymeric colorant made in accordance withthis invention is water-soluble, which property is defined to mean thatsuch a polymeric color exhibits a solubility in neutral room temperaturewater of greater than 500 parts per million weight (basis water).

Preferred anthraquinone chromophores in their unattached (monomeric)state have a leaving group such as a --CL, --Br, --I, --SO₃ Na,--N₂.sup.⊕ Cl.sup.⊖, or --NO₂ group attached to their aromatic ring.This permits the chromophore's facile attachment to the backbone aminesby the known technique wherein copper is used to catalyze the leavinggroups' displacement by amines. In many cases, no catalyst is requiredto effect the desired displacement. Representative classes of usefulanthraquinone chromophores include:

Aminoanthraquinone chromophores of the structure of Formula I; ##STR6##formed by coupling the monomer IA wherein R₁ is a hydrogen or a lowersaturated alkyl of up to four carbon atoms, R₂ is hydrogen, a lowersaturated alkyl of up to four carbon atoms or an aryl or alkaryl of fromsix to eight carbons and X is a leaving group. These are useful to givethe range of blue colorants listed in Table I.

                  TABLE I                                                         ______________________________________                                        Compound                                                                      R.sub.1    R.sub.2          Color                                             ______________________________________                                        hydrogen   hydrogen         purplish blue                                     hydrogen   methyl           greenish blue                                     hydrogen   ethyl, propyl or butyl                                                                         greenish blue                                     hydrogen   aryl             navy blue                                         ______________________________________                                    

Anthrapyridones of the structure of Formula II; ##STR7## formed bycoupling the corresponding monomer, wherein X is a leaving group, R₁ ishydrogen, a lower saturated alkyl of from 1 to 4 carbon atoms inclusive,or an aryl grouping of about 6 carbons, R₂ is a 1 to 4 carbon lowersaturated alkyl, a 1 to 4 carbon lower saturated alkoxy, or an arylgrouping of about 6 carbon atoms, and R₃ is hydrogen or a 1 to 4 carbonlower saturated alkyl. These chromophores are rich reds. Preferred amongthe anthrapyridones are these according to Formula II wherein R₁, R₂,and R₃ are as shown in Table II.

                  TABLE II                                                        ______________________________________                                        R.sub.1   R.sub.2        R.sub.3                                              ______________________________________                                        hydrogen  1-4 carbon alkyl                                                                             1-4 carbon alkyl                                     hydrogen  methyl         methyl                                               hydrogen  methoxy        1-4 carbon alkyl                                     hydrogen  methoxy        methyl                                               hydrogen  ethoxy         1-4 carbon alkyl                                     hydrogen  ethoxy         methyl                                               hydrogen  phenyl         methyl                                               methyl    methyl         hydrogen                                             methyl    phenyl         hydrogen                                             ethyl     methyl         hydrogen                                             methyl    methoxy        hydrogen                                             ethyl     methoxy        hydrogen                                             ______________________________________                                    

Anthrapyridines of the structure of Formula III: ##STR8## which areformed by coupling the corresponding monomeric chromophore ##STR9##wherein X is a leaving group, R₁ is a 1 to 4 carbon lower alkyl group oran aryl group of about 6 carbons and R₂ is hydrogen or a 1 to 4 carbonlower alkyl and R₃ is a 1 to 4 carbon alkyl group or aryl group of about6 carbons. These colorants range in hue from yellow to red. PreferablyR₂ is hydrogen or methyl. Other typical anthraquinone chromophoresinclude the pyridinoanthrones, anthrapyrimidines and anthrapyrimidones.

Among the azo chromophores, those having monomeric forms containingsulfonyl halide groups comprise one preferred class since they can jointo the amine backbone via the well-known Schotten-Baumann reaction.Exemplary azo chromophores and representative halo precursors include:

    ______________________________________                                        Chromophore       Precursor                                                   ______________________________________                                         ##STR10##                                                                                       ##STR11##                                                   ##STR12##                                                                                       ##STR13##                                                  ______________________________________                                    

The Schotten-Baumann reaction also functions with sulfonylhalide-containing nonazo chromophores such as:

    __________________________________________________________________________    Chromophore          Precursor                                                __________________________________________________________________________     ##STR14##                                                                                          ##STR15##                                                ##STR16##                                                                                          ##STR17##                                               __________________________________________________________________________

The attachment of these or other chromophores may be carried out by anyof the methods for joining a chromophore to a polymer through an aminelink known in the art. In the case of anthraquinone chromophores, it ispossible to achieve facile attachment by employing an anthraquinonebearing a leaving group attached to its aromatic ring. This leavinggroup is readily displaced by the backbone amine, generally in thepresence of a copper catalyst, such as copper metal, cuprous oxide,copper I salts (cuprous chloride, etc.), copper II salts (cupricacetate, etc.), and complexes of copper, copper oxides and/or coppersalts optionally with an inert carrier such as a carbon carrier. Thisreaction is generally carried out at an elevated temperature, such asfrom about 60° C. to about 130° C., with the solvent reflux temperatureoften being most convenient. Following reaction, it is best to filterthe reaction mixture to remove solid catalyst which could interfere inlater steps.

In another representative attachment method, an alkyl halidegroup-containing chromophore is contacted with the amine backbone underalkylation conditions. Preferred alkyl halide groups include methylchloride and methyl bromide groups. In general, no catalyst is requiredand a mixed aqueous/organic (e.g., aqueous/THF) solvent is employed.With this reaction, it is important to block any amine groups on thechromophore, such as by acetylation, prior to attachment and afterattachment unblock them.

In the Schotten-Baumann reaction coupling method a chromophore bearing asulfonyl halide group is reacted with the amine backbone in the presenceof base at pH 10-11 to form the desired covalent bond. This reactiongoes smoothly at temperatures of from 0° to 60° C. and requires fromabout 2 to 12 hours to complete. In the case of azo compounds, it shouldbe remembered that the polymer backbone with its amine groups couldinterfere with an attempt to diazotize an attached azo dye precursor.Thus, it is best when azo colors are involved, to attach a diazotizedcolor unit, rather than an undiazotized azo color precursor.

These three routes to color attachment are merely representative. Othermethods may be used if desired.

The portion of amine groups which are used to attach chromophores canvary. In general, it is desirable to have as many as possible react soas to impart the greatest possible tinctorial strength to the polymericcolorant. Often, however, it is not possible to achieve quantitativesubstitution of the amine groups. Substitution of from about 30% to 100%of the amine groups with chromophores is highly desirable to achieve atruly useful polymeric colorant. Under normal conditions, substitutionsof from about 30 to about 70% can be achieved.

USE OF COLORANTS

The colorants of this invention, being water-soluble find wideapplication for example in the fugitive coloring of textiles and in thecoloring or tinting of water-solvented or water-containing materialssuch as water-based paints and inks, hydrophillic polymers, and thelike. In an especially advantageous use, these colorants are admixedwith edible materials, such as foods, beverages, medicines and the like.In this use it is most useful to size the colorants such that theirmolecular weight is not less than about 1500, preferably from 2000 to200,000 most preferably from 5,000 to 150,000. A colorant of thismolecular weight has a molecular size which is too large to permit itsabsorption through the walls of the gastrointestinal tract and thus anyrisk of systemic toxicity arising from absorption of colorant from thegastrointestinal tract is essentially eliminated. The colorants, becauseof their carbon-carbon backbones and direct amine-linked chromophores,are essentially free of degradation at the conditions of passage throughthe gastrointestinal tract.

In nonedible applications, the colors of this invention may be usedalone or may be admixed with other colorants in amounts of from about 20ppm to 10% by weight in water-based paints, in water-soluble inks anddyes and may be applied to fibers, fabrics, paper and the like.

In applications with edible materials, the colorants are added in aneffective coloring amount, say from about 10 ppm to about 1% by weight(preferably from 10 ppm to 1000 ppm) to foods such as gelatin desserts,dispersed in dry cake mixes and cereals, added to fruits and othercanned foods, to beverages such as carbonated beverages, for exampleorange, grape and cherry soda, wines and the like; and added tomedicines such as cough elixers, cough drops and diverse other usuallycolored medicaments for man or beast alike. These applications involvethe art known procedures of dispersing, dissolving or otherwisespreading the colorant upon or through the object to be colored.

The invention will be further described by reference to the followingexamples. These are intended to provide an understanding of specificembodiments of the invention and are not to be construed as limiting theinvention's scope.

EXAMPLE I

This Example sets forth a preparation of an ethylsulfonate ethylaminecopolymer and its use in a water-soluble colorant.

A. Preparation of Vinylacetamide

To 2304 g of acetamide (technical) in a 12 liter reaction flask is added62.2 ml of 6 M aqueous sulfuric acid followed immediately by 661 g ofacetaldehyde (99+%). This mixture is stirred and heated until theinternal temperature reaches 78° C. (11 minutes) at which point theclear solution spontaneously crystallizes, causing a temperature rise to95° C. The reaction product, ethylidene-bis-acetamide, is not separated.Heating and stirring are continued for another 5 minutes to atemperature of 107° C. and a mixture of 150 g calcium carbonate(precipitated chalk) and 150 g of Celite^(R) diatomaceous earth powderis added. A first distillate fraction of water and acetamide is removed.The remaining materials are cracked at 35 mm Hg and 185° C. A fractionmade up of vinylacetamide and acetamide is taken overhead, analyzed byNMR and found to contain 720 g of vinylacetamide and 306 g of acetamide.A portion of this pooled material is dissolved in isopropanol, cooled,and filtered to yield a stock solution. This stock solution is analyzedand found to be 4.1 Molar in vinylacetamide.

B. Preparation of Copolymer

Into a five liter flask is added 280 ml (272 g) of a vinylacetamidesolution obtained by stripping isopropanol from 500 ml of the stocksolution of Part A (containing 176 g of vinyl acetamide). AIBN (6.6 g)in 100 ml of methanol is added followed by 1046 g of 25% w sodium vinylsulfonate in water (Research Organic Corp.) and a liter of water. Thisis one equivalent of sulfonate per equivalent of vinylacetamide.Following deoxygenation, the mixture is heated to 65° C. and theremaintained with stirring for 57 hours. This reaction mixture is thenreduced to 2/3 volume and added to seven liters of acetone. Thecopolymer precipitate is collected and dried in vacuum to yield 536 g ofsolid copolymer (MW 2.1×10⁴). Whenever an experimental molecular weightis given herein, it is derived by gel permeation techniques. In theprimary technique, a silanized porous glass support is used with a 0.01M LiBr in DMF eluent. Detection is by refractometer with standardizationbeing based on suitable purchased poly(styrene) orpoly(styrenesulfonate) standards.

Into a two liter flask is added 400 g of the just-noted solid product,600 ml of water and 400 ml of concentrated hydrochloric acid. Themixture is refluxed (99°-110° C.) for about 50 hours. Brine (600 ml) and60 ml of additional concentrated hydrochloric acid are added during thereaction to maintain solubility. The reaction mixture is added hot toabout twelve liters of methanol to give a fine solid precipitate whichafter drying totals 218 g. This product is examined by elementalanalysis and NMR and determined to be a 1:1±5% copolymer of sodiumethylsulfonate and ethylamine.

C. Attaching Chromophore to Copolymer

To 95 ml of water is added four grams of Na₂ CO₃ and 2.5 grams of thecopolymer of Part B. When this has dissolved, five ml of pyridine isadded followed by nine grams of the anthrapyridone chromophore,##STR18## purchased from Sandoz Color and Chemical Co. The temperatureis brought to 95° C. Cuprous oxide (2.5 g) catalyst is added. Themixture is maintained at temperature for 41/4 hours. Na₂ CO₃ is addedduring heating to maintain the pH at 10.7-10.8. The reaction mixture isfiltered, brought to pH 9 by HCl addition, combined with twelve ml ofpyridine, passed through a Sephadex column, reduced to 110 ml, passedthrough a Sephadex column again to remove unattached chromophore,stripped of solvent to dryness, dissolved in 40 mls of water at pH 7,passed through a Sephadex column again, and freeze dried to give about1.5 g of a polymeric colorant having the following structural units.##STR19## This product has a red color. This product has a peakmolecular weight of about 4×10⁴. Proton and reductive titrations arecarried out on the product. These analyses indicate that n equals about110, m equals about 60, and m' equals about 70.

D. Use of Polymeric Colorant

The product of Part C could function as a colorant for edibles or othersubstrates. It is water-soluble so it might be dissolved in soft drinks,in gelatin desserts, in cough tonics or in cake batter. It might also bedry-mixed as a powder in soft drink powders or cake mixes.

EXAMPLE II

The colorant preparation of Step C of Example I is repeated withmodifications. Instead of the purchased anthrapyridone chromophoreemployed in Example I, an equimolar amount of ##STR20## chromophore isemployed. This chromophore is prepared in a number of batches which arepooled. A representative preparation is as follows:

Into a two liter flask is placed 100 g (422 mmol) of1-amino-2-methylanthraquinone (BASF) and 500 ml of glacial acetic acid.The mixture is heated to 42° C. and 135 g (844 mmol) of bromine is addedover about 20 minutes. After stirring for 11/2 hours at 42°-56° C., thereaction mixture is filtered. The solid product is washed with aceticacid (500 ml) and water (1000 ml). The wet filter cake is added to aliter of 0.5 N NaHSO₃ and stirred for 90 minutes with warming. The redsolid 1-amino-2-methyl-4-bromoanthraquinone is recovered, washed anddried.

A 100 ml flask is charged with 12.6 g (40 mmol) of the1-amino-2-methyl-4-bromoanthraquinone, 11.4 g of ethylacetoacetate, 20.3g of nitrobenzene and 0.33 g of sodium acetate. The mixture is heated to150° C. in a 175° C. oil bath with stirring. Lower boiling materials(water, ethanol, etc.) are distilled off as they are produced. Afterheating for four hours, the reaction mixture is cooled and filtered. Theresidue is washed with methanol, water and methanol and is found to be3'-acetyl-2-methyl-4-bromo-1,9-anthrapyridone, i.e., ##STR21##

This material is coupled to the polymer backbone as follows: To 200 mlsof water are added 5.0 g of the sodium ethylsulfonate-ethylaminecopolymer of Part B of Example I, 1.17 g of NaOH, 12 g of chromophore,and 1.5 g of Cu₂ Cl₂. The mixture is refluxed for 71/2 hours.Periodically, base is added to hold the pH at 12.5-12.8. At 51/2 hours,four grams of chromophore are added. At seven hours, 1.5 grams of Cu₂Cl₂ and two grams of chromophore are added. The reaction mixture isfiltered (with added Celite® diatomaceous earth filter aid) to removesolids. The polymeric colorant is precipitated by adding methanol andethylacetate and collected. It is redissolved in water, dialyzed andfreezedried to yield a final solid product. This product is titrated todetermine the extent of chromophore attachment. About 45% of the aminegroups have joined to chromophore groups.

EXAMPLE III

This Example sets forth a preparation of3-methylpiperidine-ethylsulfonate copolymer and its use in theproduction of a polymeric colorant.

A. Preparation of Polymer Backbone

Into a 50 ml flask is added 6.2 g of diallylamine hydrochloride and 20ml of a 25% aqueous solution of sodium ethylenesulfonate (ResearchOrganics). t-Butylhydroperoxide polymerization catalyst (0.2 ml) isadded and the mixture is brought to 50°-55° C. with stirring. At 18 and24 hours 0.2 mls of additional catalyst is added. At 41 hours thereaction heat is turned off. The reaction mixture is diluted with 25 mlof water, filtered and then poured into methanol. A white precipitateforms which is dried in vacuum. Gel permeation chromatography indicatesa peak molecular weight of 6.6×10³ for the product. Titration of aminegroups indicates that 48 amine groups are present for each 52 sulfonategroups.

B. Attachment of Chromophores

The known [R. R. Pritchard et al, J. Chem. Soc., (1938) page 2047]benzanthrone sulfonyl chloride: ##STR22## (2.91 g) is stirred in 25 mlof ethylene glycol. This mixture is then combined with four ml of waterplus two ml of ethylene glycol and 2.0 g of the polymer of Part A.Additional glycol (35 ml) is added and the mixture is brought to 90° C.NaOH is added to maintain the pH at 9.8-10.0. After 45 minutes thereaction mixture is cooled, added to 100 ml of water, filtered, dialyzedagainst pH 8 water, and freeze-dried. Analysis indicates that about 1/2of the amine groups have reacted with the chromophore to yield ##STR23##groups. This is a polymeric yellow colorant. It could be added toedibles such as beverages, pharmaceuticals, and the like.

EXAMPLE IV

This Example sets forth the preparation of anN-methylethylamine-ethylsulfonate copolymer and its use in thepreparation of a polymeric colorant.

A. Preparation of Copolymer

N-methylacetamidoethylene (3.81 g) is added to 20 g of a 25% w solutionof sodium ethylene sulfonate in water. 0.32 g of AIBN is added, themixture is deoxygenated and heated to 80° C. An exotherm carries thetemperature to about 95° C. The mixture is stirred for about fiveminutes and then added to isopropanol in which a pale pink-white fluffforms. This fluff is recovered, washed with isopropanol, dried anddetermined to have a peak molecular weight of 4×10⁴. ##STR24## Thiscopolymer (6.35 g) is placed in 720 ml of 6 N hydrochloric acid andstirred at 125° C. for 68 hours. The reaction mixture is cooled, broughtto pH 3 with 2.5 N sodium hydroxide, stripped to 40 ml, filtered toremove solids, and then further stripped to yield a copious precipitatein about 20 ml of solution. Nine ml of water is added to redissolve thesolid and the solution is added to 600 ml of methanol in which anoff-white solid forms, if collected, washed and dried. NMR analysisshows that the acetamide groups have essentially all been coverted toamine groups such that the final copolymer has the structure ##STR25##B. Preparation of Chromophore

4.4 g (10 mmol) of D&C Orange #4 (Eastman): ##STR26## is reactedovernight at room temperature with an excess of acetic anhydride inpyridine to acetylate the naphthyl hydroxyl group. The acetylatedproduct is recovered and added to a solution of an excess of SOCl₂ inDMF. After stirring for two hours at room temperature, the bright orangesulfonyl chloride derivative ##STR27## is recovered. C. Coupling ofChromophore to Backbone

The backbone of Part A of this Example (1.86 g, 4.6 meq of availableamine) is dissolved in a 2:1 mixture of water and THF. Base is added topH 10. Next, 0.71 g (0.4 equivalents based on available amine present)of the chromophore of Part A is slowly added at room temperature whilemaintaining the pH at 9.0-9.5 by NaOH addition. Additional THF and NaOHare added, the pH is raised to 11.0, and finally the THF is stripped toyield the product: ##STR28## (peak molecular weight about 5×10⁴) as aprecipitate which is collected.

EXAMPLE V

A. Monomer Preparation

A three-liter stripper flask is set up, equipped with an agitator,mantle, thermocouple, feed port, argon bleed and stripping-distillationsystem. Also a glass column is charged with a kilogram ofAmberlite®IR-120 plus ion-exchange resin. The resin is activated bycontact with 10% w H₂ SO₄ and then rinsed.

A reaction flask is charged with 1.42 kg of acetamide dissolved in 1.8 lof deionized water. Then 440 g of acetaldehyde is added. This mixture isfed to the top of the column at the rate of 50-150 ml/minute. The columneluent is tested for organics. When organics begin to appear, the eluentis passed to the stripper flask where at 40-75 mm Hg absolute pressurewater and acetamide are stripped overhead.

When water and acetamide are removed (temp equals 175° C.-180° C.),Celite® 503 diatomaceous earth (100 g) and calcium carbonate are addedto the stripper flask. A 40-75 mm vacuum is applied and the temperatureis raised to 200° C.±5. This causes the ethylidene-bis acetamide formedin the contact with the ion exchange resin to crack and giveacetamidoethylene which is taken overhead and collected.

B. Copolymer Preparation

Acetamidoethylene monomer prepared in Part A (5 moles) is added to a 5liter agitated reactor along with 2.7 moles of vinylsulfonate (sodiumsalt) and 16 g of AIBN. The materials are placed in a 5 liter reactionflask and heated to 75° C. while d oxygenating the flask. Temperature isincreased to 80° C. and held there for 180 minutes. The reactionmixture, a solution of a copolymer of vinylacetamide and vinylsulfonate,is dissolved in water. This solution is purified by filtration andultrafiltration in an Amicon ultrafiltration unit in the presence ofadded NaCl. Low molecular weight impurities are removed leaving asolution of vinylacetamide-vinylsulfonate as retentate.

C. Copolymer Hydrolysis

A Teflon-lined reaction vessel is charged with 4-7 kg of 30% copolymersolution of Part B. The 50% NaOH (1-1.5 kg) is added and the reaction istaken to 90°-95° C. and then 125° C. and there held for 22 hours. Thesodium ethylsulfonate-vinylamine copolymer product is then collected.

D. Colorant Preparation

The copolymer of Part C, in amount to provide 1.6 moles of amine, isadded to a 5 liter flask. Water (2.5 l) is added and the mixture isheated to ˜99° C. Then 430 g of the chromophore of Example I and 32 g ofcuprous chloride are added. Sodium hydroxide, 170 ml of 50% solution, isgradually added. After 60 minutes the reaction is stopped. The solutionis thereafter filtered and ultrafiltered to yield a polymeric dyeproduct similar to that obtained in Example I.

What is claimed is:
 1. A copolymer comprising a plurality ofethylsulfonate and 2 to 6 carbon atom lower alkylamine groups, the sumof the number of ethylsulfonate groups and lower alkylamine groups beingfrom 20 to 8000 and the number of lower alkylamine groups being from 0.4to 2.5 times the number of ethylsulfonate groups.
 2. The copolymer ofclaim 1 wherein said copolymer is represented by the structural formula:##STR29## wherein R₁ and R₂ are independently selected from the groupconsisting of hydrogen and 1 to 4 carbon saturated alkyls, R₃ is a 1 to4 carbon saturated alkyl, R₄ is selected from the group ofcarbon-nitrogen single bond and 1 to 4 carbon lower saturated alkyls andR₁, R₂, R₃, and R₄ together contain not more than 5 carbon atoms; n andm are integers, n+m is equal to 20 to 8000, n is from 0.4 to 2.5 n andM⁺ is an alkali metal cation.
 3. The copolymer of claim 1 wherein thelower alkyl amine is ethylamine, the sum of units of ethylamine andethylsulfonate is from 20 to 8000 and the number of units of ethylsulfonate is from 0.6 to 1.5 times the number of units of ethylamine. 4.The copolymer of claim 3 wherein the alkali metal is sodium.
 5. Apolymeric colorant comprising the copolymer of claim 3 having units ofchromophoric group covalently bonded to from 30% to 70% of the units ofethylamine.
 6. The polymeric colorant of claim 5 wherein saidchromophoric group is selected from the anthraquinone and azochromophoric groups.
 7. The copolymer of claim 1 wherein the loweralkylamine is 3-methylpiperidine and the sum of units of3-methylpiperidine and ethyl sulfonate is from 20 to 8000 and the numberof units of ethyl sulfonate is from 0.6 to 1.5 times the number of unitsof 3-methylpiperidine.
 8. A polymeric colorant comprising a copolymerhaving a plurality of ethylsulfonate and 2 to 6 carbon atom loweralkylamine groups, the sum of the number of ethylsulfonate groups andlower alkylamine groups being from 20 to 8000 and the number of loweralkylamine groups being from 0.4 to 2.5 times the number ofethylsulfonate groups having a plurality of chromophoric group unitscovalently bonded thereto through said lower alkylamine groups.
 9. Thepolymeric colorant of claim 8 wherein said chromophoric groups isselected from the anthraquinone and azo chromophoric groups.
 10. Apolymeric colorant comprising a copolymer having a plurality ofrepeating units of ethylsulfonate and ethylamine the sum of the numberof units of ethylsulfonate and ethylamine being from 20 to 8000 and thenumber of ethylamine units being from 0.5 to 2.5 times the number ofethylsulfonate units and having units of chromophoric group covalentlybonded to from 30% to 70% of the units of ethylamine; said chromophoricgroup having the structure ##STR30## wherein R₁ is selected from thegroup consisting of hydrogen, a saturated alkyl of from 1 to 4 carbonatoms inclusive, and about 6 carbon aryls; R₂ is selected from the groupconsisting of 1 to 4 carbon inclusive saturated alkyls, 1 to 4 carboninclusive alkoxies and about 6 carbon aryls; and R₃ is selected from thegroup consisting of hydrogen and 1 to 4 carbon saturated alkyls.
 11. Thepolymeric colorant of claim 10 wherein R₁ is hydrogen, R₂ is methyl andR₃ is methyl.
 12. The polymeric colorant of claim 10 wherein R₁ ishydrogen, R₂ is ethoxy and R₃ is methyl.